AST 1002 Exam 1 With Complete
Solution
Looking back in distance means... - ANSWER Looking back in time
AU (Astronomical Unit) - ANSWER Distance from the Earth to the Sun
(150,000,000 km); a useful unit to measure distances within the solar system
Light-year - ANSWER Distance traveled by light in one year (10^12 km); a
useful unit to measure distances within the Milky Way and to other galaxies
The celestial sphere - ANSWER A giant "sphere" extended around the Earth
and rotating East to West
Celestial equator - ANSWER The projection of the terrestrial equator onto the
celestial sphere
Celestial poles - ANSWER Earth's rotation axis intersects the celestial sphere
at the North and South ____________
Ecliptic - ANSWER Path of the Sun in the celestial sphere over the course of a
year
Solstices - ANSWER The two times a year when the sun is at its greatest
distance from the celestial equate; The sun reaches its highest and lowest
point in the sky, marking the longest and shortest days
Summer Solstice - ANSWER The sun reaches its highest point in the sky when
it crosses the meridian around June 21
The sun rises early and sets later in the day -- the sun stays up in the sky
,longer during the summer
Winter solstice - ANSWER The sun reaches the lowest point when it crosses
the meridian on December 21
The sun rises late and sets earlies -- stays up in the sky for a shorter period
Equinoxes - ANSWER Where the Sun crosses the celestial equator twice a
year; at the vernal equinox around March 21st and the autumnal equinox
around September 21st
Autumnal Equinox - ANSWER Around September 21st
Vernal Equinox - ANSWER Around March 21st
The celestial coordinates - ANSWER The projection of the terrestrial
coordinate system of longitude and latitudes on the celestial sphere
generates the set of celestial coordinates.
The _____________ are called Right Ascension (RA) and Declination (Dec or dec)
Right Ascension - ANSWER Time to rotate through a given angle (The angle
is measured in hours-minutes-sec); longitude; Range of values: 0 to 24 hours
Declination - ANSWER Angle in degrees north/south of the Celestial equator;
latitude; Range of values: 0 to +90 and 0 to -90 degrees
Reference for Declination - ANSWER 0 degrees of Dec is at the Celestial
equator
Reference for Right Ascension - ANSWER 0 hours of RA is at the position
where the Celestial equator crosses the Ecliptic
Constellations - ANSWER Random configurations of stars
,There are 88 in the sky
Usually not close together
Solar days - ANSWER 24 hours (one rotation of the Earth relative to the Sun)
Sidereal days - ANSWER 23 hr 56min (one rotation of the Earth relative to a
reference star)
The reason for the seasons - ANSWER The 23.5 degrees tilt of the Earth's
rotational axis
Colder temperatures in the winter are a result of: - ANSWER Sun stays lower
in the sky during the day (sunlight less direct).
Sun is above the horizon for shorter periods (shorter days).
Lunar Phases - ANSWER
Relative positions of Earth-Moon-Sun and phases of the Moon Lunar Phases -
ANSWER refer to image in PPT
Tilt of the Moon orbital plane respect to the Earth orbital plane - ANSWER
The Moon's orbital plane is tilted 5 degrees to the ecliptic (plane in which
Earth orbits the Sun)
What is precession? - ANSWER period is 26,000 years;The slow change in the
direction of the rotation axis of a spinning object, caused by some external
gravitational influence
What is parallax? - ANSWER The apparent displacement of the foreground
object (pencil) respect to the background as the observer's location changes
(distance between eyeballs)
Solar eclipse - ANSWER The Moon blocks the Sun's light from the Earth
, (Coincidentally, the Moon and Sun have the same angular size, around 0.5
degrees!)
•The phase of the Moon must be new Moon
• Solar eclipses can only be seen from specific places on Earth
•Three types of solar eclipses: Total, partial and annular
Lunar eclipse - ANSWER •The Earth blocks the Sun's light from the Moon
•The Sun and the Moon must be in opposite direction as seen from Earth
•The phase of the moon must be full Moon
•Can be seen from anywhere on the Earth where the Moon is visible
Full moon - ANSWER We only see the illuminated half area of the moon
(sunlight->earth->moon)
New moon - ANSWER We only see the dark half area of the moon
(sunlight->moon->earth)
If a star has a Declination of +40 degrees, in which celestial hemisphere is it
located and how far the celestial equator? - ANSWER Northern hemisphere --
40 degrees
Solution
Looking back in distance means... - ANSWER Looking back in time
AU (Astronomical Unit) - ANSWER Distance from the Earth to the Sun
(150,000,000 km); a useful unit to measure distances within the solar system
Light-year - ANSWER Distance traveled by light in one year (10^12 km); a
useful unit to measure distances within the Milky Way and to other galaxies
The celestial sphere - ANSWER A giant "sphere" extended around the Earth
and rotating East to West
Celestial equator - ANSWER The projection of the terrestrial equator onto the
celestial sphere
Celestial poles - ANSWER Earth's rotation axis intersects the celestial sphere
at the North and South ____________
Ecliptic - ANSWER Path of the Sun in the celestial sphere over the course of a
year
Solstices - ANSWER The two times a year when the sun is at its greatest
distance from the celestial equate; The sun reaches its highest and lowest
point in the sky, marking the longest and shortest days
Summer Solstice - ANSWER The sun reaches its highest point in the sky when
it crosses the meridian around June 21
The sun rises early and sets later in the day -- the sun stays up in the sky
,longer during the summer
Winter solstice - ANSWER The sun reaches the lowest point when it crosses
the meridian on December 21
The sun rises late and sets earlies -- stays up in the sky for a shorter period
Equinoxes - ANSWER Where the Sun crosses the celestial equator twice a
year; at the vernal equinox around March 21st and the autumnal equinox
around September 21st
Autumnal Equinox - ANSWER Around September 21st
Vernal Equinox - ANSWER Around March 21st
The celestial coordinates - ANSWER The projection of the terrestrial
coordinate system of longitude and latitudes on the celestial sphere
generates the set of celestial coordinates.
The _____________ are called Right Ascension (RA) and Declination (Dec or dec)
Right Ascension - ANSWER Time to rotate through a given angle (The angle
is measured in hours-minutes-sec); longitude; Range of values: 0 to 24 hours
Declination - ANSWER Angle in degrees north/south of the Celestial equator;
latitude; Range of values: 0 to +90 and 0 to -90 degrees
Reference for Declination - ANSWER 0 degrees of Dec is at the Celestial
equator
Reference for Right Ascension - ANSWER 0 hours of RA is at the position
where the Celestial equator crosses the Ecliptic
Constellations - ANSWER Random configurations of stars
,There are 88 in the sky
Usually not close together
Solar days - ANSWER 24 hours (one rotation of the Earth relative to the Sun)
Sidereal days - ANSWER 23 hr 56min (one rotation of the Earth relative to a
reference star)
The reason for the seasons - ANSWER The 23.5 degrees tilt of the Earth's
rotational axis
Colder temperatures in the winter are a result of: - ANSWER Sun stays lower
in the sky during the day (sunlight less direct).
Sun is above the horizon for shorter periods (shorter days).
Lunar Phases - ANSWER
Relative positions of Earth-Moon-Sun and phases of the Moon Lunar Phases -
ANSWER refer to image in PPT
Tilt of the Moon orbital plane respect to the Earth orbital plane - ANSWER
The Moon's orbital plane is tilted 5 degrees to the ecliptic (plane in which
Earth orbits the Sun)
What is precession? - ANSWER period is 26,000 years;The slow change in the
direction of the rotation axis of a spinning object, caused by some external
gravitational influence
What is parallax? - ANSWER The apparent displacement of the foreground
object (pencil) respect to the background as the observer's location changes
(distance between eyeballs)
Solar eclipse - ANSWER The Moon blocks the Sun's light from the Earth
, (Coincidentally, the Moon and Sun have the same angular size, around 0.5
degrees!)
•The phase of the Moon must be new Moon
• Solar eclipses can only be seen from specific places on Earth
•Three types of solar eclipses: Total, partial and annular
Lunar eclipse - ANSWER •The Earth blocks the Sun's light from the Moon
•The Sun and the Moon must be in opposite direction as seen from Earth
•The phase of the moon must be full Moon
•Can be seen from anywhere on the Earth where the Moon is visible
Full moon - ANSWER We only see the illuminated half area of the moon
(sunlight->earth->moon)
New moon - ANSWER We only see the dark half area of the moon
(sunlight->moon->earth)
If a star has a Declination of +40 degrees, in which celestial hemisphere is it
located and how far the celestial equator? - ANSWER Northern hemisphere --
40 degrees
